Many diseases are associated with abnormal pressure changes. Early detection of these changes is therefore important. At present the current state of the clinical medical art is to be able to detect only advanced pressure changes due to progression of frequently fatal disease processes. Accordingly, there is a need for early detection implantable devices to assess and follow changes in both acute and chronic references based in terms of days to years, and to provide a serial, comparable method for permanent recording and comparison. Such pressure monitoring systems require three stages: sensor, transducer, and quantitative recording.
The invention is concerned with devices for monitoring the pressure of various body fluids, such as in the central nervous system, genito-urinary and cardiovascular systems. One important application of such devices is the measurement of intracranial pressure. It is desirable to determine, for example, if an abnormal amount of pressure exists in such areas as the bladder, vena cava, intracranial ventricles and under the dura in the cranial cavity, and other areas. Various practices have been attempted with varying degrees of success for measuring such body pressure.
To date the methods used in the art are based on direct puncture and hydraulic measurement methods; implantable devices using a balanced force principle; piezo-electric crystal; fiberoptic pressure sensing; or radioactive detection chamber. All of these practices have serious disadvantages such as high cost.
There is a need to provide a reliable body pressure monitor which controls problems attendant with the prior art such as drift. There is further a need to provide such a monitor which can be utilized with minimum inconvenience to the patient a repeated number of times. There is likewise a need for a monitor which also provides a permanent record of the information upon which the body fluid pressure measurements are taken.